Absolutely! You can cancel your plan at any time. You'll be entitled to your services until your next billing date, when your services will stop.
The lowdown:
Log in to the app and go to the Your Profile section (top right icon)
Go to the Cancel your plan section and follow the instructions.
Alternatively you can cancel your plan by logging in to your account at https://simpmobile.com/login
🔔 Keep in mind that whilst cancelling is completely free, you will lose all your coins and unredeemed rewards.